Integration of the 660 MW supercritical steam cycle with the NH3-based CO2 capture process: System integration mechanism and general correlation of energy penalty

Aqueous ammonia based post-combustion CO2 capture (PCC) is an attractive alternative to amine based technologies for reduction of CO2 emission from coal fired power stations. However its integration with power stations is not well studied. This research examined the system integration mechanism of the 660 MW supercritical steam cycle with a NH3-based PCC process. Three integration methods were proposed:Method 1 (steam extraction from the IP/LP crossover), Method: 2 (steam extraction from the IP/LP crossover and the addition of a new letdown turbine while the condensate is returned to the deaerator), and Method: 3 (steam extraction from the IP/LP crossover and addition of a new turbine while the condensate is returned to the condenser). Three cases were presented using the above three methods, and were designated as Case 1, Case 2, and Case 3, respectively. The original power plant was taken as the base case. Among three cases studied, the thermal efficiency of case 2 is the highest and at 36.08% with a decrease of thermal efficiency by 11.61 percentage points compared to the base case. A sensitivity analysis was performed to investigate the effect of important parameters including the concentration of NH3, CO2 loading, and stripper pressure on the regeneration duty of the capture process and the energy output of the integrated process. The minimum energy requirements of the capture process does not lead to the minimum energy penalty introduced on the power plant. The findings indicate that the energy penalty in PCC integrated power plant depends on the temperature of the extracted steam, the heat duty of the reboiler, and the stripper pressure. A general correlation of the energy penalty of ammonia based PCC onto a supercritical power plant was obtained from the simulation results, which can enable a reliable evaluation of the PCC energy penalty imposed on the power plant.